Method of producing solid soap products from potash soaps and products obtained thereby



March 13, 1956 M SHEELY ErAl.

METHOD OF' PRODUCING SOLID SOAP PRODUCTS. FROM POTASH SOAPS AND PRODUCTSOBTAINED THEREBY Filed Jan. 24, 1952 wtkbu /VENyRSI BY @M c.' d/lATTURNE Y United States Patent epesses METHD F PRDUClNG SOLID SOAP PROD-UCTS FRQM PTASH SOAPS AND PRODUCTS BTAHNED THEREBY Madison L. Sheely,Western Springs, and Emmett P.

Glynn, Chicago, lll., assignors to Armour and Company, Chicago, lll., acorporation of Illinois Application .lanuary 24, 1952, Serial No.268,114

6 Claims. (Cl. 252--368) This invention relates to a method of producingsolid soap products from potash soaps, and to the products produced bythe method. This invention has particular utility in producing solidpotash soap in the form of bars, chips, and granules.

Soap can be defined as a salt of one or more of the higher fatty acidswith an alkali or metal. Most soaps are made by the action of sodium orpotassium hydroxide on fats and oils. The potassium and sodium soaps arecommonly referred to respectively as potash and soda soaps. When soapsare prepared directly from the raw oils or fats by the-use of potassiumor sodium hydroxide the reaction is referred to as saponiiication, sinceit involves the splitting of the triglycerides of the fatty acids toform glycerin and the alkali metal salts of the fatty acids found in theparticular oil or fat. Soap can also be made by a neutralizationreaction between sodium or potassium hydroxide and free fatty acids,which are obtained from the fats or oils by various processes.Therefore, for purposes of convenience, soaps composed of potassiumsalts of the fatty acids will be referred to hereinafter as potassiumsoaps, while soaps composed of sodium salts of fatty acids will bereferred to as sodium soaps. It will therefore be apparent that bothsodium and potassium soaps can be prepared by saponiication orneutralization reactions, depending on whether the starting materialcontains the triglycerides or the free fatty acids.

At the present time, commercial solid soap products are mainly sodiumsoaps. In fact, nearly all solid soaps, and in particular lsolid soapsin the form of bars and granules, are composedejntirely of sodium soaps.However, in the case of solid soap in the form of haltes, it is thegeneral practice, especially in the case of the ne fabric flakes, toincorporate at least l0 but not over 30% by weight potassium soaps toimprove the solubility of the sodium soaps, and to decrease thebrittleness ofthe chips.

In the production of soaps, and in particular solid soaps, the main fatemployed is tallow, while coconut oil is also extensively used. Tallowis a much less expensive raw material than coconut oil, and therefore itwould be desired to use tallow exclusively, if it were possible to do soand obtain a satisfactory product. However, it has been found necessaryto combine between l0 and 35% by weight coconut oil soaps with thetallow soaps to enhance the solubility and sudsing characteristics ofthe tallow base soaps. t v

Potassium soaps are commonly referred to as soft soaps, because of theirgreat anity for water, and because they are prepared and marketed intheform of liquid or paste soap products, rather than' in the form of hardsoaps. For example, liquid soaps for use in dispensers are usually madefrom coconut oil using 100% caustic potash saponification. So-calledgreen soaps are paste products made with soft oilsor fatty acids and100% caustic potash saponiiication. usually contain substantialpercentages of coconut oil Shaving creams and hard fats or fatty acidssaponied with caustic potash. With the exception of soap flakes orchips, mentioned above, hard soap products are not formulated with anypotassium soaps, and even in the case of soap chips only a minorproportion of potassium soaps are combined with the sodium soaps.

Probably the primary reason for the failure of the soap industry tomarket potassium base soaps in solid form is due to theirhygroscopicity. This defect of potassium soaps has long been recognized.They have a much greater ainity for water than sodium soaps, and tend totake up Water from the atmosphere when exposed thereto.`

Also, in bar form, potassium soaps tend tosoften excessively on contactwith water. When potassium soaps are prepared in the form of chips orgranules, the greater area of exposed surface accentuates the effect ofthe hygroscopic tendency of the soap. However, aside from this defect,the potassium soaps have desirable properties which are comparable toand in some ways superior to sodium soaps. For example, potassium soapsgo into aqueous solution at much lower temperatures than sodium soaps. v

lt is therefore an object of this invention to provide a method forproducing potash soaps in the form of solid soap products which willovercome the objectionable hygroscopic tendency of potassium soaps. ltis a further object of this invention to develop modifications in theprocedure of manufacturingsodium soap products which will allow thesolid potassium soap products to be prepared with the same equipment.Further objects and advantages will appear as the specication proceeds.

This invention is based on the discovery that by reducing the moisturecontent of solid potassium base soaps below a critical value that theobjectionable hygroscopic tendency of the soap material is substantiallyeliminated regardless of the extent of the surface area of the soapexposed to the atmosphere, with the result that when potassium soaps aredried below this critical limit they can be marketed in any desiredform, such as bars, chips, and granules.

Heretofore, it has been the practice to prepare solid soap products in amanner that will assure that the n'al solid soap product contains arelatively high percentage of Water. For example, toilet soap in barform and washing soap in granule form Acontain between l0 to 15%moisture; soap in the form of chips contains from l() to 20% moisture;and laundry soap in bar form contains up to 30% moisture. lt can bestated in general that solid sodium soaps must contain at least about10% water to give satisfactory results in both manufacturing andcommercial use. This amount of water is required in the soap duringprocessing to allow the milling operations to be carried out Withouthardening and pou/dering the soap. Also, if the finished productcontained less than about 10% water, it would not be suiiicientlysoluble to give satisfactory results under ordinary conditions of use.

During the experimental work leadingV to this invention, it had beendetermined that potassium soaps containing an amount of watercorresponding to the amount allowed to remain in sodium soaps cannot beused to produce satisfactory solid soap products, such as bars, chips,and granules. When solid potassium soap products are formulated in a`similar manner to sodium soap products they are found to exhibit anobjectionable hygroscopic tendency. However, it has nowbeen determinedthat if the moisture content of thepotassium soap` is reduced to atleast 4% and preferably to 3.5% by weight o-r below, that theobjectionable hygroscopic tendency of the soap is substantiallyeliminated. This appears to be true regardless of the extent of thesurface area of the soap exposed to the atmosphere. Therefore, byreducing the moisture content of potassium soapv to at and granules.

water. 'Within' the crutcher, and thoroughv mixing of the soap therein,the molten soap is flowed onto a chilled roll 12, which is generallyassociated with a small roll (not shown) several rotatably-mountedcylindrical drums. v lindricaldrums or rolls areso' mounted that thesoap from the'dry'er 14 is passedon t`o the rolls. These rolls exert apressing and polishing action on the dried ribleast 4%', Athe soapcanfbe marketed in any desired form,`

such as bar, chips, and, granules. While-the moisture content ,canY bereduced to a very. low value,` say 1%, with satisfactory results, itisbelieved that completely anhy- .drous potassiumsoaps are not asfdesirable as the potassium soaps containinga critically small amount ofmoisjture.

Therefore, it isdesired that the potassium soaps contain vfrom about 1to 4% moisture, and preferably between about 210.35% moisture. n a

' Although the experience Withsolid sodium soaps would have indicatedthat the reduction of the water coutent "of potassium soaps to lessthanY 4% would have rendered the normal milling procedures, extremelydifficult, this l p has not proven to be the case. v,Potassium soapscontainling less than. 4% moisture can be milled according to the usualprocedures Without undue hardening or powdering ofY the soap. Also, ithas been determined that the reductionlof the vmoisture content doesnot-unduly Vim-` ing shows a typicalow sheet in simplified form foriythe preparation of solid soap products; namely, bars,-chips, In theillustration given, the potassium hydroxide and tallow fatty acids areshown being charged to a crutcher 11,7which is a special type ofsteam-jacketed agitator. 'Potassium soaps can also beprepared bysaponification ofy the triglycerides, butV special and relativelyexpensive procedures are' required to separate the 'glycerinel Ylf asubstantial amountof glycerine Was left inthe soap, it would defeat thepurpose 'of the present 'inventiongsince glycerinehas been found toaffect the vhygroscopicity of potash soaps in a manner similar to Uponthe completion of the chemical reactionsV which together roll the soapinto` a large flaty sheet about the large roll. This sheet ofsoap isthen cut into ribbons' by a serieslof metal protrusions on the doctor#knife 1.3.- Thesefribbons areV removed by the doctor knife and conveyedto a dryer 14, in Whichthe moisture content of the soap is reduced tothev desired value for the subsequent'operations and in the `finishedproduct.

After'the ribbonsA of soapvare driedto the desired moisturejcontentfthey are either passed to an yamalgamatoril or tofa'mill 16,depending onwhether it is desired to form the ribbons into bars orchips. If bars are desired, the ribbons are passed to the amalgamator n15, which is a specialized type of `mixer in which perfume v and othersubstances canfbe added. Upon leaving the amalgamator the soap ispassedthrough a series of devices which further knead and mix the soap.These may take the formv of mill rolls 17 and screw conveyor 18.

- Upon leaving theup'per end of screw V.conveyor 18,

the soap-is extruded through avdie extruder `member19.

',The .extruded soap `is thenrfurther processed to produce the finished`bars* by cutting at 2,0, pressing at 21, and wrapping atr22. Y

lf chips or flakes are desired` instead of bars, the dried l ribbons arepassed from .dryer 14 to mill 16.

y In-the illustration Agiven, the mill is indicatedy as consisting, of

These cybons lfv desired, this mill may be equipped to take ythe flakesoff 'as -`ribbons or, if desired, in a diamond shape. From the mill thefinished chips or flakes are passed to packaging at 23.

The preparation of granules follows a somewhat different procedure inthat the molten soap from crutcher 11 is passedVV to a spray tower 24.The molten soap is sprayed into the top of the tower and allowed to falldownwardly -against'a stream of warm dry air moving upwardly within thetower. This forms the drops of of soap. By regulating the temperatureand volume of the air how through thetower, it is possible to producegranules having the desired moisture content.

`vWhile the above discussion of the processing of soap is considerablysimplified, it does set forth the important steps inthe process whichparticularly yrelate to the present invention.'

It is now desired to discuss the modifications required in theprocessing of potassium soap on conventional equipment of the typeillustrated in the drawing from that `used for sodium soap.

The same fatty starting materials can be employed forf producingpotassium soaps as for producing sodium soaps. For example, tallow orcoconut oil can be employed, or the free fatty acids 'derived'therefrom. Tallow Vis composed mainly of triglycerides of-fatty acidscontaining from 16 to 1S carbon atoms. As high as 40 to k50% of thefatty acidsV in tallow-may be unsaturated The saturated fatty acidsfound-in tallow are mainlypalmitic and stearic, while the unsaturatedacids are oleic and ylinoleic. The .fatty acid composition of coconutoil is somewhat different in that the main fatty acids found therein,contain from l2tol V14 carbon atoms.. These acids are respectivelymyristic and lauric. Therefore, it can be seen that a mixture of thepotassium salts of'coconut fatty acids andtallow fatty acids Will becomposed mainly of Vpotassium salts of fatty acids containing fromA 1 2to 18 4 carbon atoms. f

As a resulty of the investigations leading to this invention, it hasbeen discovered vthat potassium soaps prepared exclusivelyfrom tallowfatty acids have properties which are VVsubstantially the equivalent ofthe ordinary commercial grades of sodium soaps which are tallow basesoaps but in addition contain from 10 to 30% of coconut oil soap. Inviewofthe much greater cost of coconut oil compared toftallow, itispreferred to prepare the potassium base soaps of this inventionexclusively from tallow. These potassium base soaps can be formedentirely of potassium soap, or can contain a minor proportionofsodiumsoaps. However, there does not .appear to be 4any particularadvantage'in combining the sodium andpotassium soaps, since thepotassium soaps, when*V dried in accordance with `this invention, are nomore `hyg'roscopic lthan similar. sodium soaps, and .are otherwise theequivalent of the sodium soaps in such proper ties as detergency, sudsvolume, and solubility. In addition, the potassium soap possesses theYadvantage of being able Vto go into solution at a considerably lowertemperatureV than the sodiumsoap. l

It has been found that there is another factor which has some eifect onthe hygroscopicity of the potassium soaps. This factor is 'the titer ofthe fatty raw material. TiterV isa standard test for fats and oilsinwhich the sample is completelyisaponiiied, and `the solidifying pointl `(or titer) of the resulting separated and washed fatty acids aredetermined. In preparing solid vpotassium soaps fronrtallow, it has beendeterminedthat when the tallow has a. relatively high titer thehygroscopic tendency of the finished soap is somewhat reduced. The-titerof tallow or other fat can be increased by hydrogenation,

if its titer is lower than desirable. Also, a mixture having thedesiredtiter can be prepared by the mixing of a low-,titer stockv with ahigh titer stock. Generallylin the titer of the tallow at least 40 C.and preferably Vat least 43 C. Completely hardened tallow s undesirable,and it is probable that it will not be desirable to use tallow having atiter much above 50 C. The optimum range is from about 43 to 47 C.

In the processing of sodium soaps, it is the general practice to havefrom 32 to 34% moisture in the molten soap when it is in the crutcher.For some reason, which is not clearly understood, it has been found thateven at this early point in the processing of the potassium soaps it isvery desirable to have the moisture content reduced to at least 23% andpreferably to 21%. The moisture content of the soap in the crutcher canbe regulated by controlling the amount of water charged to the crutcher,or by evaporating some of the water from the molten soap. By keeping themoisture content of the melted soap in the crutcher below 23%, it hasbeen found that there is a considerable increase in the jell strength ofthe material, which assists in forming the soap on the chilled roll.

In the applying of melted sodium soaps to the surface of a chilled rollto form a sheet thereon, it is generally suthcient to have the surfaceof the chilled roll at a temperature between about 62 and 68 F. Thistemperature range, however, has proven to be much too high in processingpotassium soaps. To achieve satisfactory results, it is preferable tohave the temperature of the chilled roll below about 40 F. For example,the cold water used to chill the roll can be supplied at a temperatureof between 35 and 40 F.

As indicated above, in preparing solid potassium soaps the majordeparture from the procedure used in preparing solid sodium soaps is thedrying of the potassium soaps to less than about 4% moisture content.The reasons for drying the soap to below this critical moisture contenthave already been discussed. It will be apparent from an examination ofthe flow sheet shown in the accompanying drawing that when the potassiumsoap is to be formed into bars or chips that the required drying of thesoap can easily be carried out in the dryer to which the soap is passedin the form of ribbons. Also,

when the potassium soap is to be prepared in the form of granules, thetemperature and volume of drying air passed through the spray tower canbe adjusted to give the required moisture content.

In order to better illustrate this invention, it is desired to set outthe following illustrative example.

Example Employing equipment similar to that illustrated in the flowsheet of the drawing, 1,000 pounds of tallow fatty acids having a titerat 45 C. was charged to the crutcher together with suicient potassiumhydroxide to completely neutralize the acids. After the completion ofthe neutralization reaction, the molten soap containing around 21%moisture was thoroughly mixed. Part of the molten soap was then appliedto the usual chilled roll which was maintained at a temperature ofbetween about 35 to 40 F. The sheet of soap on the chilled roll was cutinto ribbons by the usual procedure and passed to a dryer in which itsmoisture content was reduced to about 3.5%. Finished chips and nishedbars were then prepared from the dried ribbons according to the usualprocedures. The rest of the molten soap was passed from the crutcher toa spray tower in which it was formed into granules by the usualprocedure. The temperature and volume of the drying air were adjusted toproduce a moisture content of about 3.5 in the nished granules.

'I'he finished bars, chips, and granules were tested to determine theirproperties. A standard commercial sodium base soap was used forcomparison containing 79% tallow soap and 21% coco soap. The titer ofthe combined tallow and coconut oil prior to saponication was 39 C. Itwas found that the potassium soap showed equal or slightly superiordetergency on wool and cotton to the standard commercial sodium soap. Inanother comparison test, the potassium soap showed approximately equalsuds value to the commercial sodium soap. However, in a solubility test,the potassium soap proved to be slightly more soluble than the sodiumsoap.

The hygroscopicity of the potassium soap in the form of bars, chips, andgranules was determined by exposure of the solid products to a moistatmosphere, and it was determined that they were no more hygroscopicthan the standard commercial sodium base soap in the same form.

The investigations leading to this invention have conrmed that solidpotassium soaps have a number of important advantages over theconventional solid sodium soaps. One of these advantages is that whendirt is removed from a surface by the action of a potassium soap, it ismuch less likely to be redeposited on the surface than when sodium soapis used. In other words, the redeposition factors of potassium soaps arein general considerably lower than sodium soaps. Another importantadvantage of potassium soaps is that they can be used with a high degreeof effectiveness in sea water, as compared to sodium soaps.

As indicated above, it has been determined that solid potassium soapsmade exclusively from the fatty acids of tallow do not suffer from thesame disadvantages as sodium soaps prepared exclusively from tallow. Itis therefore unnecessary to employ coconut oil fatty acids to produce agood solid product of potassium soap. Potassium soaps preparedexclusively from tallow fatty acids possess certain resultant orcollateral advantages. One of these is that they are less irritating tothe skin, since coconut oil fatty acids tend to be more irritating thantallow fatty acids. A further advantage of potassium soaps preparedwithout the use of` coconut oil fatty acids is that the production ofgood soap is rendered independent of imported raw materials. All of thecoconut oil required to meet the domestic demand must be imported intothe United States. With the present world situation it can be readilyappreciated that a technological advance permitting high quality solidsoaps to be prepared without the use of coconut oil represents animportant contribution to the economy.

While in the foregoing specification specific details of this inventionhave been set forth for purposes of illustration, it will be readilyapparent to those skilled in the art that many of these details can bevaried widely without departing from the spirit of our invention.

We claim:

l. The method of producing a solid soap product from tallow fatty acids,comprising converting tallow fatty acids having a titer of at least 40C. to their potassium salts to obtain a potassium tallow soap containingconsiderably greater than 4% by weight of water, reducing the watercontent of said potassium tallow soap to within the range of 1 to 4%water by weight, and forming said potassium tallow soap into a solidsoap product in marketable condition, said solid soap product beingcomposed substantially entirely of said potassium tallow soap whilebeing substantially non-hygroscopic.

2. The method of producing a solid soap product from tallow fatty acids,comprising converting tallow fatty acids having a titer of from 43 to 47C. to their potassium salts to obtain a potassium tallow soap containingconsiderably greater than 4% by weight of water, reducing the Watercontent of said potassium tallow soap to within the range from 2 to 3.5%water by weight, and forming said potassium tallow soap into a solidsoap product in marketable conditon, said solid soap product beingcomposed substantially entirely of said potassium tallow soap whilebeing substantially non-hygroscopic.

3. A solid soap product in marketable form, consisting substantiallyentirely of potassium tallow soap composed of potassium salts of tallowfatty acids having a titer of at least '40?, C. in admixture with from(1 to 4% by weight of water.L n Y c 4.A solid soap product inmarketable'form, consisting substantiallyA entirely "of potassium tallowsoap coml vposed of potassium saltso` tallow fatty acidshaving a titeroffrono 43 to 47 C. in admxture with from 2 to 3.5% by Weight of Water.

5. rIhe method of claim 1 in which said` potassium tallow sdoap prior tosaid water-reducing step is irl the form yof a molten materialVcontaining less than 23%' water by weight,land is further processed byapplying said molten Y material tothe surface of a chilled roll to formasheet thereon, cutting said sheet to obtain ribbons of said matef rial,and performing the water-reduction step of said claim l by drying saidribbons.

Y8 i The method of claim 5 in which saidchilled roll is maintained ataternperature betweeny about 35 to 40 F.

during'the applicationjof said soap materalthereto.

References Cited inthe'filc of this patent` YUNITEDv STATES PATENTS2,087,788 Thal V K. July 2o, 1937 V2,594,956 Marshall Apr. 29, 1952FOREIGN PATENTS 486,819 Greatn'lain June 1o,4 1938 VOTHER REFERENCESSer. No.`107,398, Welter (A. P.VC.), publishedMayl 24, i

3. A SOLID SOAP PRODUCT IN MARKETABLE FORM, CONSISTING SUBSTANTIALLY ENTIRELY OF POTASSIUM TALLOW SOAP COMPOSED OF POTASSIUM SALTS OF TALLOW FATTY ACIDS HAVING A TITER OF AT LEAST 40* C. IN ADMIXTURE WITH FROM 1 TO 4% BY WEIGHT OF WATER. 